Ducman82

sexy!

Tom in Austin

Cool stuff! While you're educating us about cranks ... what is a 'knife edge' crank?

SMTCapeCod

counterbalancing weights are designed/machined to a finer edge to reduce windage.

If the correct neurons are firing from my halcyon hotrod days.

GlenL

So these are "billet" and not cast. Amazing work and commitment.

What goals were there in the design? Addressing the well-known oil passage problem, to be sure!

SMTCapeCod

Located a little photo essay with visuals on some crankshaft machining techniques.

http://www.turbomagazine.com/tech/06.../photo_02.html

Don't know that I'd want to be among the first to lighten counterweights and risk harmonics given the 928 block material and configuration. Chamfering the oil holes is key though...wasn't that the one of the 'solutions' for the roasting bearings years ago? It was like some big epiphany, despite having been done on bowtie blocks for a few decades? (as well as accusump, and reserve resevoirs)...

SMTCapeCod

I would expect--
Built to closer initial tolerances,
Eliminates casting imperfections and flashing that can foster cracks
Lighter
Stronger- particularly given hardening process.
Probably an interesting discussion to be had about the analysis to determine correct degree of hardening vs. elasticity/resilience for the desired rpm range.

FredR

Always great to see an artist at work!

Fred

Shane

Are you using Reardon Steel, I heard that stuff was unsafe...

GregBBRD

Well, hopefully so. Tough to tell, since none of the lightening holes are drilled. Getting mass off of the "rod" throw determines how much counterweight you need, so we've worked at reducing that mass.

My goal is to remove 5 lbs. off of "each" difference stroke crankshaft. Anything more than that would be an "extra" bonus.

GregBBRD

I'm having 3 different strokes made. One stroke for 5.0, one stroke for 5.4, and one stroke for 6.5 liters. All of the connecting rods are already built and ready to use...just waiting for cranks. The cranks will come completely balanced for use with my rods and stock pistons (in the case of the 5.0 and 5.4 cranks) and pre-balanced to my rods and my pistons, for the 6.5 liter engines.

The idea was to give the high performance 5.0 guys and 5.4 guys a "drop in" alternative to "re-drilling" a stock crank, significantly providing a much, much stronger rod, while being able to use a much "harder" rod bearing. Seems like every one of these engines that get assembled, for high performance use, suffer from "multiple rod bearing failures". People get tired of these failures and simply "give up. The '93 GTS engines have weak connecting rods that need to be replaced, so these people are "halfway" to the point of needing a complete "uber" crankshaft and rod assembly, anyway. Plus, these "smaller" 5.0and 5.4 engines are to the point of being able to "twist" their engines to higher rpms, but are limited by rod bearings, crank weight, crank flex, etc.

These cranks will be a minimum of 50% stiffer than the stock cranks.

GregBBRD

My "target" price point is slightly higher than a current stroker crank, of course. Crank prices really have not changed prices since Marc Thomas was selling Scat cranks.

I'm still waiting to get the "final" bills, but it looks like I will be able to offer these "uber" cranks for under $4,000. This price will not repay me for the significant "developmental and engineering" fees that the crank builder charged me, for quite some time. Those costs will have to be spread over many years.

Speedtoys

Hint: Buy the crank, then buy Gregg a high end hooker to cover overhead.

GregBBRD

Actually, part of the reason for doing this was to help with the pounding that the blocks are taking, in high performance use. I've seen a few cracked blocks, from this pounding.

A lighter, stiffer crank is a huge step forward towards reducing the load on these blocks....not making it worse, as you are thinking.

GregBBRD

Yes, billet. My current Moldex cranks are also billet. The Moldex crank that I order is a very high quality piece of steel, with very high quality control and made to exacting standards. I id not have any problems with my Moldex cranks...I just thought that it was time to "update" things, a bit.

Remember, every crank that we touch, as 928 engine people, was designed over 20 years ago. To say "things have changed in engine design over the past 20 years", would be a huge understatement.

So, there were many goals, which is why I threw the old design away and sat down with a brand new crank builder. I didn't want to "drag" any old , tired ideas into the equation. We sat down with a blank sheet of paper and started from there.

* Lighter
* Stiffer
* Better material
* Current counterweight design
* Improved oiling
* Large selection of rod bearing types, to suit individual customer needs.
* Local machining, so I could be "involved" with design and quality.
* Higher rpm potential
* Reduced Harmonics
* Plus two more very significant goals, that I'm simply not able to reveal, at this time.

GregBBRD

"Knife edge" is a term that appeared many years ago, in crank building. Basically, the leading edge of the counterweight was brought to a shape that resembled the shape of a huge knife. This was found to reduce windage, as the crank spins. This shape "gave way" to the more current completely rounded leading edge, which actually "creates" less windage than a sharper edge.

Some people still "cling" to the idea of using a "knife edge" on the trailing edge of a counterweight, but many think that a rounded edge works better, here also. The reality is that the oil is moving so fast on the counterweight, by the time it reaches the end, that it can't possibly conform to the shape of a 'knife edge" and probably simply flies straight off.

Some argue that an airplane wing is rounded on the front and is more "knife edge" shaped at the rear. The problem with this logic is that an airplace wing starts tapering to that "knife edge" almost immediately after the rounded edge cuts through the wind, not quickly terminated, like on a crank counterweight. The other problem with comparing an airplane wing to a crankshaft is that the crankshaft is turning through a virtually "solid" wall of oil at higher rpms.